Data Rate of EGPRS is Too Low

Hi all, I have set up the EGPRS network using software bundles (osmo-nitb + osmo-bts-trx + osmo-trx + osmo-pcu + osmo-sgsn + openggsn) based on the USRP B210 platform. Now the cell phone can connect to the EGPRS network, but the network is not stable and the data rate is too low (only about 8kbs). Is this data rate correct? If not, could you pls send me some working config files? Thank you. Best Regards, Xinke